For this case, the first thing we must do is define a variable.
We have then:
x: number of weeks
y: amount of cereal that Melanie eats
We now write the function that models the problem:

Then, for 5 weeks we have:
Answer:
A model that best represents the number of pounds of cereal she eats is:
For 5 weeks we have:
18% = 0.18
Tip = $36.00 x 0.18 = $6.48
Total bill = $36.00 + $6.48 = $42.48
Answer:
Total bill = $42.48
Tip = $6.48
You make a bar and you take 34 and shade 18. Count the squares not shaded.
Don't take my word on this. I may be wrong.
Hmm
let's try some numbers
we have 3 scenarios
x>y
x=y
x<y
x>y
x=-1 and y=-2
x-y=-1-(-2)=-1+2=1
it's positive when x>y
x=y
x=-1, y=-1
-1-(-1)=-1+1=0
nope
x<y
x=-2 and y=-1
-2-(-1)=-2+1=-1
nope
x-y is positive when 0>x>y